Electrical control system



Dec. 1, 1964 3,159,824

L. BODDY ELECTRICAL CONTROL SYSTEM 4 Sheets-Sheet 1 Original Filed Sept. 23, 1955 INVENTOR. 18071.47 1

Dec. 1, 1964 L. BODDY 3,159,824

ELECTRICAL CONTROL SYSTEM Original Filed Sept. 23; 1955 4 Sheets-Sheet 2 Dec. 1, 1964 L. BODDY ELECTRICAL CONTROL SYSTEM 4 Sheets-Sheet 3 Original Filed Sept. 23, 1955 INVENTOR.

- dim/EM Dec. 1, 1964- BODDY 3,159,824

ELECTRICAL CONTROL SYSTEM Original Filed Sept. 23, 195 5 4 Sheets-Sheet 4 a 4 3 if! 1 1 if; 55

2; I f) 1&5 &2 24; if; 114 1* X 1/1 1W 2m- 1% I Ffi 1, 2 3%: 1x134 r I I 370 K H l Z I! 2124 INVENTOR.

AGOWdTZ j y United States Patent iC 3,159,824 ELEQTREQAL CQNTRQL SYSTEM Leonard Buddy, Ann Arbor, Miclu, assigner to King- Seeley Thermos (30., Ann Arbor, Mich, a corporation of Michigan Original application Sept. 23, 1955, Ser. No. 536,160, new Patent No. 3,010,997, dated Nov. 21, 1961. Divided and this application Get. 9, i961, Ser. No. 143,69

17 Claims. (Cl. 34tl-2l3) This application is a division of my application Serial No. 536,160, filed September 23, 1955, now Patent No. 3,010,097.

This invention relates to signaling and control devices, and to signaling and control apparatus embodying such devices.

In general, devices embodying certain of the principles of the present invention comprise a movable element the position of which is controlled by means responsive to a plurality of input conditions. in the disclosed representative arrangements, these devices are thermally actuated, the movable element being bendable or deflectable in response to applied heat. One or more heater windings disposed in heat-transfer relationship with tie movable element serve to translate the input conditions into heat to control the movable element.

In accordance with the principles of the invention, where plural windings are provided, the energization of one of the plural heater windings tends to cause the movable element to deflect or be moved in one direction, whereas the energization of another one of those windings tends to cause the movable element to deflect or be moved in another, normally opposite, direction. Thus, in the devices exemplarily disclosed, the movable element comprises two interconnected polymetallic portions, one end of one of those portions being effectively fixed against movement relative to a reference surface and one end of the other of those portions being eliectively movable with respect to the reference surface. in a two-winding control arrangement, each of the two windings is effectively individual to each of the movable-element portions. The bidirectional action in response to applied heat may be accomplished by selecting the angle between the two per-- tions or by reversing the constituent metallic strips between the two portions.

The movable element may be adapted to impart a mechanical motion to a device to be controlled, or may carry one or more electrical contacts mateable with one or more electrical contacts in order to produce a plurality of discrete electrical output indications. In either case, the relationships between the element, the windings, and other circuitry may be selected so that the deflectable or movable element will produce an output indication in response to either of two discrete input conditions, will produce an output indication only in response to an input condition, or input conditions, of a preselected nature, amplitude, duration or incidence, will produce an output indication only if one of two input signals exceeds the other in amplitude or duration or a combination thereof, will produce two different and discrete output indications in response to two different input signals, will produce a different output indication in response to each of two alternatively received input signals and will produce a still different output indication either if neither signal is received or if both signals are concurrently received, or will produce an output indication or indications in response to other selected input conditions.

The input signals may be interrelated in any appropriate fashion and may, in fact, be related to and controlled by the output indication of the device. The relative effectiveness of any group of input signals may be selected by proportioning the plural heater windings, by

3,159,824 Patented Dec. 1, 1964 adjusting the defiectability or length of the several portions of the movable elements, or by controlling the rate of transfer of heat to and/or from the portions of the movable element.

The principles of the invention may be pragmatically embodied in a plurality of types of signaling and control circuits. Thus, in the particular examples disclosed herein, devices constructed in accordance with the principles of the present invention may be employed to sense the existence of a selected critical condition or conditions in an electrical system (such as the electrical system of any automobile), to signal the existence of that condition, and to periodically interrupt the transmission of the output signal to increase its effectiveness in merting he who is in control of the equipment, such as the driver of the vehicle. The devices may also be employed as integrating relays responsive to a signal produced by a signaling relay in a gauging circuit to produce an output indication of the existence of a critical condition by actuating an alarm device, and possessing the additional capability of automatically testing the operability of the alarm devl e even though the sensible critical condition may not exist.

The principles of the invention may also be applied to the provision of a self-voltage-compensating signaling relay in a gauging system. In another form, the principles of the invention are excmplarily applied to improve the performance of a servo mechanism.

A fuller appreciation of the principles of the invention may be obtained from the following detailed description of embodiments of the invention when read with reference to the accompanying drawings in which:

FIG. 1 is a fragmentary diagrammatic representation of a condition-responsive signaling or control system embodying the principles of the present invention, with means being provided for producing a flashing or recur ring output indication;

FIG. 2 is a fragmentary diagrammatic View of a system similar to that represented in FIG. 1 but employing a different form of signaling relay;

FIG. 3 is a fragmentary diagrammatic representation of a combined gauging and signaling system including a relay structure adapted both to act as a delay or integrating means and to automatically test the operability of the output, indicating means;

FIG. 4 is a fragmentary diagrammatic representation of alternative gauging systems, with a voltage-compensated signaling relay interposed the voltage source and the gauging sub-circuit and adapted to sense a critical condition signified by high gaugingcircuit current;

FIG. 5 is a fragmentary diagrammatic representation of a system similar to that of FIG. 4 but with the signaling relay being inserted in a branch of the gauging circuit;

FIG. 6 is a fragmentary diagrammatic representation of a gauging system, with a voltage-compensated signaling relay interposed the voltage source and the gauging sub-circuit and adapted to sense a critical condition signified by low gauging-circuit current;

FIG. 7 is a fragmentary diagrammatic representation of an arrangement similar to that of FIG. 6 but with the signaling relay being inserted in a branch of the gauging circuit and with means being provided to vary the effective insertion impedance of the signaling relay;

FIG. 8 is a fragmentary diagrammatic view of a remote control system embodying the principles of the present invention;

FIG. 9 is a top plan view of a mechanism physically incorporating the elements represented within the dottedline portion of FIG. 8;

FIG. 10 is a side elevational view of the structure of FIG. 9; and

FIG. 11 is an end elevational view of the structure of FIG. 9.

The relay structure represented in FIG. 1 of the drawings (as well as in FIGS. 3 to 8) is exemplarily disclosed as being of the type in which ambient-temperature compensation is accomplished by forming a bimetallic, tri metallic or, generally, polymetallic element into a generally U shape, with the interjoining crosspiece being formed, flanged, or reinforced so as to be relatively inflexible and unresponsive to temperature changes. Elements of this general nature are disclosed in detail in their structural environment in my copending application Serial No. 138,249, filed January 12, 1950, now Patent 2,762,997, granted September 11, 1956, as well as, in a different structural environment, in FIGS. 9-11 of the drawings hereof.

Referring to FIG. 1 of the drawings, relay it) comprises a pair of bimetallic, trimetallic or polymetallic legs 12 and 14 disposed generally in spaced parallelism with one another, with one end of one of the legs joined to one end of the other by a crosspiece 16. Means such as an upturned flange 18 is provided to prevent effective bending of the crosspiece 16 in response to heat applied thereto. For convenience of illustration, the operating element of relay 110 is shown to be bimetallic, that is, it comprises two intimately associated sheets or strips of metal having disparate temperature coetficients of linear expansion. While other arrangements be employed, in the disclosed arrangement, the entire upper surface is of one metal and the entire lower surface is of another, it being assumed, for purposes of illustration, that the metal on the lower surface of the unit has a higher temperature coefiicient of linear expansion than the metal on the upper surface.

The end 2% of leg 12 is rendered immobile with respect to some reference surface (not shown) in any suitable manner. This immobility is signified in this figure (and in the other figures of the drawings) by a symbol such as the earth symbol 22 on FIG. 1. Two such symbols on any one figure may, but need not, denote the same reference surface. This fixing or immobilizing of the end 2-9 of the leg 12 is preferably such that leg 12 is elfectively mounted substantially as a cantilever.

If the temperature of leg 12 is raised, that leg will tend to become arcuate in form, with the left-hand end thereof rising relative to that reference surface with respect to which the end 2t is fixed. As a result, crosspiece will be tilted upward, its upper surface remaining roughly tangential to the curve defined by the upper surface of the adjacent end of leg 12. If leg 14 remains straight, with its upper surface coplanar, with the upper surfaces of crosspiece 16, then it will be perceived that the right-hand end of leg 14 will be effectively moved downward. Thus, contact 24, mounted upon the righthand end of leg 14, will be moved downward away from contact 26 which is adjustably fixed with respect to the same surface as is the end of leg 12. Suitable ad justing means, if provided, may be of the form disclosed in my copending application Serial No. 526,190, filed August 3, 1955, now Patent No. 2,833,889, issued May 6, 1958.

Leg 14 may be considered to be mounted as a cantilever, in efifect, upon the crosspiece 16. If the temperature of leg 14 is changed, that leg will also tend to assume an arcuate shape, with the right-hand end thereof moving upward with respect to the reference surface to move contact 24 toward contact 26. Hence, the effect of applying heat to raise the temperature of leg 12 is to move contact 24 away from contact 26, whereas the effect of applying heat to leg 14 is to move contact 24 toward contact 2-5. The position of contact 24 with respect to contact 26 will, therefore, be determined by the temperature of both legs 12 and 14.

As a modification of the described, arrangement, the

entire bimetallic element 10 may be pivotally mounted about a transverse axis extending longitudinally of the crosspiece 1o, fixing the end Zll of the leg 12 either as shown or by merely providing stops for preventing rotation of that end 2d, such as in the manner disclosed, for example, in J. W. Anderson Patent No. 1,885,054. Similarly, control of the characteristics of the device may be established by varying the relative lengths of the legs 12 and 114-, by inserting nondefiective portions in or on those legs, by reinforcing one or both of the legs, and so on, such as is taught in my copending application Serial No. 526,190, filed August 3, 1955, now Patent No. 2,833,889, issued May 6, 1958. It will also be appreciated that the length of the crosspiece 16 is not critical and may, in fact, be reduced to zero length, with leg 14 forming an acute angle with leg 12 in order that those egs, in deflecting, will not interfere with one another. It will also be appreciated that neither leg has to be perpendicular to the crosspiece and that the two legs need not be parallel.

In the arrangement disclosed in PEG. 1, the legs 12 and 7.4 are shown to be straight on the basis that there is no present application of applied heat to either leg and that the ambient temperature level is exactly that at which the element lii'l was designed to have both of its legs straight. it will be appreciated that the characteristics of the element ill may be so selected that if both legs 12 and 14 are at the same temperature, the relationship between contacts and will be the same, regardless of that temperature, whereby true ambient temperature is achieved. Conversely, as noted, the relationships may be modified to produce any desired change of the relationship between contacts 24 and 25 upon change in ambient temperature.

Contacts 24 and 26 are normally closed, that is, regardless of the ambient temperature, those contacts are in engagement so long as no voltage is applied across either coil 23, effectively individual to leg 12, or coil 30, effectively individual to leg 14. .Vhile it will be recognized that as a practical matter the heat generated by coil 3G will affect leg 12 and the heat generated by coil 23 will affect coil 14 due to heat transfer by radiation or convection, or by conduction through the crosspiece 15, the primary effect of coil 30 is to control the emperature of leg 14 and the primary eliect of coil 28 is to control the temperature of leg 12, and hereinafter in the specification reference will be made only to the primary heating effect of the several coils, the spurious or ancillary heat transier being disregarded for clarity of description.

The system of FIG. 1 (and the other disclosed systerns) may be employed for either signaling or control purposes, and the term signaling is intended to eric to both concepts.

A suitable source of voltage (such as the storage battery of an automobile or the complete voltage-supply system of an automobile including the generator, battery, and voltage-regulator, current-regulator and cutout asembly) is connectable through a switch 36, which may he an automobiles ignition switch, to conductor 38, which is mechanic-ally and electrically secured to the element 16). Hence, upon the closure of switch as, the entire element lid is at a potential above-ground level, it being recognized that the mechanically fixing symbols, such as symbol 22, do not connote an electrical ground. Que end of heating winding 28 is connected to leg 12, and hence to the source of potential, and the other end of that winding is connected to conductor Conductor 4% is, in turn, connected to a plurality of paralleled resistors 42:, 44 and as, each of which is connected in series with an individual condition-responsive switch 48, or 52, to ground.

Switches 48-52 are actuated by means (not shown) responsive to an individual critical condition of any suitable nature. For example, if the principles are to be be genapplied to an automotive electrical system, switch 48 may be normally closed and adapted to be opened if the gasoline supply reaches a preselected minimum level, switch St is normally closed and may be adapted to open, for example, in response to the reduction in oil pressure or the automobile to a preselected minimum value, and switch 52 may similarly be adapted to open in response to any selected critical condition such as the attainment of a selected high coolant temperature or the reduction in coolant level below a preselected value.

If the sensed conditions are normal at the time that switch 36 is closed, current may flow from the potential source through the Winding 28 and to ground over a relatively low-impedance path comprising resistors l2-46 in parallel. The resultant relatively high current magnitude through heating winding 23 will result in substantial deflection of the leg 12, tending to produce a tilting of the crosspiece 16 and a resultant downward movement (as represented in PEG. 1) of the right-hand end of leg 14 to move contact 24 in a direction away from contact 26.

One end of heater winding 36 is electrically integral with leg 14 and, hence, is connectable to the voltage source 34 upon the closure of switch 36. The other end of heater winding 3% is connected to fixed contact 26 and then to ground through the filament of lamp 253, which is intended to be but representative of any suitable alarm or control device. By virtue of this connection, with contacts 24 and 26 open, under the normal initial conditions, current will flow through the heater winding 3d and the filament of the lamp 33 in series. Depending upon the relative values of these two elements, lamp 33 will glow dimly or not at ll. The current through winding 39 will produce an elevation of the temperature of leg 14 to cause the right-hand end thereof to deflect upward, in a direction tending to bring contact 24 into engagement with contact 26. Whether contact 24 will actually engage contact 26, in response to the initial closure of switch 36, depends upon the condition of contacts 4842 and upon the relative rate of temperature elevation of leg 14- and leg 12. if all of the contacts 4852 are closed when switch 36 is first closed, then whether contact 24 engages contact initially is a matter for individual selection. Thus, if the rate of initial deflection of leg 12 is great relativ to the rate of initial deflection of leg 14, contacts 24 and 26 will not be brought into engagement upon the closure of switch 35. On the other hand, if the rate of initial deflection of leg 14 is great relative to the rate of ini tial deflection of leg 2, contact 24 will engage contact 26. When this occurs, leg 14 and contacts 2d-26 will constitute a low-impedance shunt across winding 3% lamp 33 will be brightly illuminated, and windin 3% will commence to cool. This initial bright illumination of lamp 33 will serve as an indication to the person controlling the system with which the disclosed apparatus is associated, such as the driver of the vehicle, that the signaling system is operative and, more particularly, that lamp 33 is in operating condition.

The cooling of winding 39 will permit leg 14 to cool and separate contact from contact 2s. Continuing on the assumption that contacts 48-52 are all closed, the parameters may be so selected that by this time leg 12 will be adequately heated to prevent any re-engagemerit of contact 24- with contact 2*. However, if desired, repetitive initial flashing of tie lamp 33 may be accomplished. Thus, upon the separation of contact 24 from contact 26, due to the shunting of winding 30, the lowimpedance shunt across winding 3!) will be relieved, wind ing 5t? will again heat to deflect leg 14- to bring contact 24- again into engagement with contact 26 to again fully energize lamp 33 and to again shunt winding $3. This repetitive flashing will recur until such time as winding 28 has sufficiently deflected leg 14 so that contact 24 can no longer engage contact 26.

Under either arrangement, once leg 12 has been adequately heated, the system will remain in this condition until such time as one or more of the condition-responsive switches 4t5-52 is opened in response to the attainment of the individual critical condition. Upon the opening of any one or more of the contacts 48 to 52, the total impedance of the circuit is increased due to the deletion of one or more of the parallel paths including resistors d2, 44 and 46. The value of resistors 42, 4d and as are so selected that, upon the opening of any one or more of the contacts 4-8, 5-1 and 52, the reduction in current through heater winding 28 will be such that leg 12; will adequately cool to permit contact 24 to move into engagement with contact 25, this engagement occurring since heater winding Ed is energized.

This closure of contacts 24 and 26 will produce a shunting of heater winding 3% and a full energization of lamp 353 to signal the existence of the trouble condition. The shunting of the winding 3d will permit leg 14 to cool to separate contact from contact 26, which will rte-establish the energizing circuit for winding 36 and reduce the energization of lamp 33. The re-establishment of the energizing circuit for winding lit? will cause a reheating of leg 14 to again bring contact 24 into engagement with contact 26, and so forth, with lamp 33 repetitively flashing between a bright and dim intensity or between a bright intensity and extinction.

This repetitive flashing of alarm device 33 will continue until such time as switch 36 is opened or until the trouble condition is corrected so that contacts 48, 5t) and 52 are again all closed.

It will be appreciated that the arrangement of FIG. 1 (as well as of FlG. 2) can be modified so that relay 1t) senses and is responsive to high-current rather than lowcurrent conditions and that, in that case, the lower ends of resistors 4-2 to td may be connected directly to ground, with the condition-responsive contacts 43 to 52 being normally open and connected in shunt of their individual resistors. Gther modifications will be apparent to those skilled in the art.

The arrangement of PEG. 2 of the drawings is electrically and functionally identical to the arrangement of FIG. 1 and the corresponding electrical elements are correspondingly identified, the reference characters applied to the elements of FIG. 2 being distinguished by a prime. In the arrangement of FIG. 2, however, the element 10' is shown to be rectilinear and to be divided into two portions, with the direction of deflection of the two pertions bein opposite to one another in response to applied heat. Thus, element it? comprises portions 56 and 58 rigidly interjoined in alignment with, and in extension of, one another. Each of the portions 56 and 5% comprises two elongated strips of metal intimately interjoined along their abutting faces. In the representative arrangement shown, the metal on the lower surface of portion 56 has a higher coeiiicient of linear expansion than the metal on the upper surface of that portion, whereas the metal on the upper surface of portion 58 has a higher coefficient of linear expansion than the metal on the lower surface of that portion. The metal on the lower surface of portion 56 may, but need not, be the same as the metal on the upper surface of portion 53; and the metal on the upper surface of portion 56 may, but need not, be the same as the metal on the lower surface of portion 58.

The left-hand end of portion 56 is immobilized with respect to the reference surface and the right-hand end of portion 58 carries the contact 24. If winding 28 upon portion 56 is energized, elevating the temperature of portion 56, the right-hand end of Lhat portion will tend to deflect upwardly, thereby tending to move portion 58 and contact 24 upwardly away from contact 2". Conversely, if winding Bil upon portion 58 is energized to apply heat primarily to portion 5%, portion 58 will tend to bend with its right-hand end moving downwardly to carry contact 2% towar contact 26. Hence, windings amass i 28' and 3% tend to move contact 24- in opposite direc tions, just as was the case with the U-shaped element, or modifications thereof, represented in FIG. 1 of the drawings.

The operation of the arrangement of FIG. 2 is identical to that of FIG. 1 and will not be redescribed.

It will be appreciated that element of FIG. 2 may be modified within the scope of the present invention. Thus, a transverse pivotal axis may be established by means, for example, of a pivot pin supported with respect to the reference surface and supporting the pclyrnetallic element at the line of junction of portions 5'6 and 58, the axis of rotation lying in a piane parallel with the upper and lower surfaces of the portions 56 and 58. Some means should he provided to limit the travel of the lefthand end of portion 56 without interfering with the pivotal action of the bimetal. Other arrangements performing equivalent functions will be apparent to those skilled in the art.

It will be noted that, in the exemplary systems of FIGS. 1 and 2, the relay serves as a signaling device and a flasher, and may also serve a lamp-proving function.

In the arrangement of FIG. 1, the element It? is representatively provided with a pair of normally-open contacts. The arrangement of FIG. 3 demonstrates that a similar element may be provided with a pair of normallyclosed contacts, and further demonstrates the use of a bi-directionally moving element in a gauging and signaling system. The representative gauging circuit depicted in FIG. 3 of the drawings comprises a sender of a gauge 62 and a source of potential 64 which may, for example, be the battery or the battery-generator-regulator combination of an automobile. A signaling relay 66 is inserted in the series gauging circuit which may be traced from source of potential or, switch 68 (which may be the automobiles ignition switch), polymetallic element '79 and winding 72 of signaling relay as, conductor 74, heater winding 76 of gauging element 62, heater element '73 of sender 6i and through contacts 88 and 32. to ground. Sender 6% is representatively shown to be responsive to the level of fuel in a gasoline tank as sensed by a float 3d.

The operation of the gauging and signaling arrangement thus far described is or may be identical to that of the system disclosed in my Patent No. 2,625,595, granted January 13, 1953, and, in accordance with that disclosure, signaling relay 66 hereof may he provided with mateable contacts 86 and as adapted to modify and regulate the effective insertion impedance of the signaling relay 66.

In general, as is described in that patent, the magnitude of the current through winding '72 of signaling relay so will be controlled by the sender so, with the amplitude of that current varying as an inverse function of the amount of gasoline in the tank. If there is more than a preselected critical quantity of gasoline in the tank, heater winding '72 of signaling relay as will he suificiently energized to cause contact 9'13 to separate from contact 92, the latter of which is either fixed with respect to a reference surface, as represented, or is adjustably fixed with respect to that reference surface. Due to the thermal nature of signaling relay so, that relay in itself tends to perform an integrating function so that transient movements of the gasoline in the tank, as reflected in transient movements of the float 84, will not tend to substantially change the condition of signaling relay 66, that relay tending to reflect average levels of the float 84 over finite periods of time.

If the gasoline level reaches the preselected critical value, the current through winding 72 of signaling relay 66 will be reduced to the point where the polymetallic element '76 will cool adequately to permit contact 9% to re-engage contact 92, thereby to connect the source of potential s4 through the element 70 to contact 92 and conductor 94.

The output of relay as is a change on the potential of conductor 3 4. Thus, since contacts 9% and 92. are closed when switch 63 is open, at the instant of closure of switch 63 substantially the full potential of source 64 will be applied to conductor 94. If the gasoline supply is adequate, contact it? will be separated from contact 92, after a heating interval, to disconnect conductor 94 from the source of potential 64. If the supply of gasoline is low when switch 68 is closed, contact 9% will not be separated from the contact 92 and the source of potential 6- will continuously be connected to conductor 94. If the supply of gasoline is initially adequate but subsequently drops to the preselected critical value, contact dd will reclose to contact 92 to again apply the potential from source as to conductor 94.

While, as noted, signaling relay 66 does tend to perform an integrating function, in practice it is frequently desirable to provide further integrating means to insure that a signal denoting the attainment of a critical condition is not transmitted unless a critical condition does, in fact, exist during the course of operation of the vehicle or the associated system. Such separate integrating means are shown, for example, in the referenced Patent No. 2,625,- 595, as shown that patent, any such integrating means may be shared in common by a plurality of ganging and signaling relay circuits. Thus, in the arrangement of FIG. 3, additional gauging and signaling relay circuits can he provided, with the other signaling-relay contacts correlative to contact 92 being multiplied to conductor 94.

Relay 96 serves, in addition to another function, an integrating function. That element comprises a first leg portion fiS, the end Hill of which is fixed with respect to a reference surface, a crosspiece 162 rendered relatively inflexible by means such as a flange 164, and a leg portion 1%, one end of which is effectively integral with the crosspiece ltlZ. Again, this arrangement is but repreesntative and may be modified within the scope of the invention, suggested modifications being previously noted with reference to FIG. 1 of the drawings.

The free end of leg 1th: carries an electrical contact 1% mateable with a contact 11% which is fixed or adjustably fixed with respect to the reference surface. Leg )8 is provided with a heater winding 112 adapted to apply 7 heat primarily to leg 98, and leg 1% is provided with a heater winding 114- adapted to apply heat primarily to leg 106. In this arrangement, it is assumed that the metal on the upper surface of element has a greater coefficient of linear expansion than the metal on the lower surface. As a consequence, elevating the temperature of leg 98 will tend to cause the non-fixed end thereof to move downwardly (in the representation of FIG. 3), so moving and tilting crosspiece UB2 that the position of leg portion 106 is changed in a direction to separate contact 108 from contact 110. Conversely, the application of heat to leg 1% will tend to cause that leg to become deformed or bent to move contact 18% toward contact 1ft].

With switch 68 open and with temperature equalization having occurred, contact 10% is in engagement with con tact 118. Hence, upon the closure of switch 68, the source of potential 64 is connected via conductor 118, through contacts 1114i and 108, leg 1%, crosspiece 102, leg 98, conductor 120, and through alarm or control device 122 to ground, alarm or control device 122 being respresentatively shown to be a lamp. It will be appreciated that the point of connection of conductor to the bimetallic portion of element 96 is not important from an electrical standpoint, since the electrical resistance of the bior polymetallic portion of that element is normally very low, particularly if a trimetallic member is employed to obtain improved conductivity.

By virtue of the completion of the described circuit, immediately the closure of switch 63, lamp 122 will be fully illuminated to indicate to the operator of the vehicle that the lamp 122 is in operating condition.

Additionally, upon the initial closure of switch 63, current will flow through heater winding 112, connected between conductor 118 and ground, and current will also fiow through element 70, contacts 90 and 92, conductor 94, and through winding 114 to ground. The effect of the application of heat to leg 106 by winding 114 is to maintain contact 103 in engagement with contact 110, in spite of the opposing eifect of the application of heat to leg 98 by winding 112. Hence, lamp 122 will remain illuminated.

Assuming that there is an adequate supply of gasoline, after an appropriate heating interval, signaling relay 66 will open contact 90 from contact 92, as previously described, resulting in the de-energization of heater winding 114 of relay 96. The resultant reduction in temperature of leg or portion 166 toward the ambient level, coupled with the fact that leg 98 is at an elevated temperature, will cause contact 108 to be separated from contact 110, interrupting the previously traced energizing circuit for lamp 122. whereupon that lamp becomes extinguished.

The apparatus continues in this condition as long as Winding 114 remains de-energized, contact 1% being held out of engagement with contact 110 by the continuing energization of winding 112. If a critical signal condition subsequently occurs, such as the reduction in gasoline level below the preselected critical level, voltage is again applied to conductor 94 by the closure of contact 9% of relay 66 to contact 92, and portion 166 of element 96 is again deflected to bring contact 108 into engagement with contact Ill) to recomplete the energizing circuit for lamp 122 to signal the existence of the critical condition. The signal will continue until the critical condition is relieved or until switch 68 is opened. Thus, element 96 includes a pair of normally closed contacts and serves the conjoint functions of an integrating relay and a lampproving relay.

Electrical gauges are customarily adapted to measure levels of and changes in voltage, current or power. In the development of gauging circuits for automobiles and certain other similar applications, the accuracy of gauging is affected by the fact that the source voltage tends to vary. While modern automobiles conventionally include a regulating unit for controlling the voltage output of the supply system including the battery and the generator, the percentage variation of this output voltage is such that a simple gauging device will prove insufficiently accurate properly to perform its function, since it reflects the changes in the supply voltage. In systems of the type shown in the referenced Patent No. 2,625,595, the sending units themselves are designed to tend to compensate for variations in the supply voltage. In other systems, such as those disclosed in my copending application Serial No. 138,249, filed January 12, 1950, now Patent No. 2,762,997, granted September 11, 1956, a separate voltage-regulating device is provided intermediate the gauging systems and the main source of voltage so that the average or mean effective value of the voltage applied to the gauging circuits is substantially constant. In still other systems, electro-magnetic gauging devices are employed having two coils in quadrature and conjointly controlling the position of a movable vane element. In practice, both of these windings are connected to reflect the value of the supply voltage but to so act in opposition upon the vane that variations in supply voltage are effectively canceled.

In order to interpose a signaling relay in a gauging circuit of the last noted type, some means must be provided for rendering that signal relay, per se, substantially insensitive to supply-voltage variations. Otherwise, even though the gauging element is capable of providing a substantially accurate reading despite variations in supply voltage, the signaling relay, intended to be responsive to a critical condition of the apparatus with which the ganging system is associated, will tend to vary in its operation as a function of the variations in the supply voltage. The arrangements of FIGS. 4-7 are designed to properly sig nal the existence of a critical condition even though the ltl voltage of the source or supply varies over a substantial range.

In certain of the electromagnetic or galvanometer type gauging systems employed in or known to the art, the existence of a critical condition is denoted by high current amplitude in the gauging circuit, whereas in other such systems the existence of a critical condition is denoted by low current amplitude. The arrangements of FIGS. 4 and 5 demonstrate the application of the principles of the present invention to high-current-arnplitude critical condition systems and the arrangements of FIGS. 6 and 7 relate to systems in which the critical condition is denoted by low current amplitudes. In the arrangements of FIGS. 4 and 6, the signaling relay is interposed the source and the remaining elements of the gauging subcircuit, Whereas in the arrangements of FIGS. 5 and 7, the signaling relay is interposed the gauging device and the sender or transmitter, that is, the signaling relay is inserted in the signaling branch.

In each case, the basic gauging circuit, without a signaling relay, comprises a simple series circuit including a source of voltage, a switch, one winding of the dual-winding gauging device, and a variable resistance element, the resistance of that element varying as a function of some condition to be sensed. An additional circuit is provided including the source of potential, the switch and the other Winding of the dual-winding gauging device to provide for voltage-variation compensation. Thus, in the arrangement of FIG. 4-, a typical temperature-responsive gauging system might include a source of potential 14%, a switch 142, conductor 144 connected directly to conductor T146 (contrary to the present showing), winding 14 8 of gauging device 159 and resistor 152 which has a negative temperature coeilicient of resistance so that its resistance decreases as its temperature increases, resistor 152 being disposed in a position to sense the tern erature, for example, of the coolant in an automobile. The other Winding 154 of the dual-winding gauging device 150 is connected betweenconductor 146 and ground so that, in a pure gauging system, winding 154 would be directly across the voltage source Mil. Hence, variations in the source 1443 would aiiect both the current through the winding 15% and the current through the Winding 148, with their effects upon the moving vane being so proportioned that the voltage variations are canceled. In this system, since the resistance of element T152 decreases with temperature, the current through conductor 14d and winding 148 will be at a value approaching its maximum value when a critical condition of high coolant temperature exists.

While coils 148 and 154 are in parallel with the source in the described arrangement, they may also be placed in series with one another across the voltage source, as is exemplified by the gasoline-level measuring system alternatively represented in FIG. 4 of the drawings. Thus, the gauging circuit, per se (omitting the signaling relay), in such a system would include a source of potential 144i, switch 142, conductor 144 connected directly to conductor 156 (contrary to the showing of FIG. 4), winding 158 of the dual-winding gauging device 160, one branch path comprising the other winding 162 thereof, and another branch path comprising resistor 164. The effective value of resistor 164 is determined by the position of float 166 which is disposed in the gasoline tank. Low gasoline level causes the resistance of resistor 164 to be reduced toward a minimum value so that the current through conductor 156 and winding 15% will approach a maximum value as the critical condition to be sensed is reached.

In either case, winding 16%; of signal relay 170 is inserted in series with the gauging circuit and between the source of potential and the gauging device or ltiil. Thus, in the representative arrangement, conductor 144 is electrically integral with leg or portion 172 of signaling relay 170, leg 172 being electrically and mechanically oneness integral with crosspiece 1'74 and leg portion 176. One end of winding 163 on leg 176 is connected to leg 1'76 and hence, electrically, to conductor M4, and the other end of winding 168 is connected to conductor 178 which is connected either to conductor 146 or conductor T155 in accordance with the particular gauging system selected. Hence, the current through winding 163 will vary as a function of the variations in current through winding 14th or winding 158 and will approach a relatively hi h value at the critical condition, the existence of which is to be signaled. While the interposition in the gauging circuit or" an additional resistance, represented by winding 168, will tend to affect the functioning of the gauging circuit, the fact that it is a maximum signal condition which is to be sensed permits the resistance of the winding 16% to have a very low value and still be capable of developing suflicient wattage at the signaling condition to adequately elevate the temperature of leg 176 of signaling relay li t This resistance may, in fact, be so low as to produce no substantial inaccuracy in the gauging circuit even without readjustment of the gauge, at the critical, high-current condition, and, of course, its effect over the entire range of normal conditions will be less.

Specifically, the value of resistor 152 approaches a minimum as the temperature of the coolant approaches the critical high level. At any lower temperature, the resistance of sensing element 152 is greater. Hence, at any temperature below the critical emperature to be sensed, the percentage of the total circuit resistance which is represented by winding 168 is less than it is at the critical condition. Similarly, the percentage of the total circuit resistance in the cn'cuit, including heater winding 168, winding 15;; and resistor 16 is greater at the critical condition of low fuel level than it is at any other fuel-level condition. Therefore, the maximum error in the gauge reading due to the insertion of the signal relay 17% in the circuit will occur at the critical signal condition, and this error will be small, even though not compensated for by modification or adjustment of the gauge, due to the relatively low value or resistance of the winding 168.

The forward end 189 of portion 172 of relay 17% is fixed relative to a reference surface. The metal on the upper surface of the bior polymetallic element is as sumed to have a hi her coefiicient of linear expansion than the metal on the lower surface so that the application of heat to leg 172 will tend to move contact 16?. away from contact 384, whereas the application of heat to winding 168 will tend to move contact 1823 toward contact 18d.

Winding ran on leg 172 is connected between conductor 1 4-4 and ground, and hence the entire source voltage is applied thereacross. An increase in the effective voltage of the source 1 th will produce an increased heating of leg 1'72 tending to further separate contact 182 from contact 1.84, but the same increase in source voltage will also produce an increased current through winding res, and hence an increased heating of leg 176, tending to force contact 18?. toward contact The converse is true in the case of reduction of the effective value of the voltage of source 134%. By appropriate selection of the circuit parameters and appropriate design of the relay 170, these variations in source voltage may be eiiectively compensated so that there is substantially no movement of contact 182 relative to contact 184 with variations in source voltage over an expected range. It will be noted that the relay 1'70 is or may be ambient temperature compensated by virtue of its construction.

In the event that the current through winding 63 in creases to the preselected value as the result of the temperature of the coolant rising to the selected critical value or the level of the gasoline falling to the selected critical value, portion 176 will be deflected to bring contact 182 into engagement with contact 18 2-, whereupon the source voltage will be applied across winding 1% or" integrating relay I192. It contact 162, remains closed to contact 134 for the appropriate selected time interval, or if, in a preselected total time interval, contact 132 is closed to contact 134 for a sufficient percentage of the time, integrating relay 192 will operate to bring the normally separated contacts 3194 and 1% into engagement with one another to apply the voltage of source 14% across the indicating, alarm or control device 193, representatively shown to be a lamp. Lamp 1% will continue to be operated until such time as the critical condition is rectified or the switch 142 is opened.

Those elements of FIG. 5 corresponding to elements of FIG. 4 are correspondingly identified except for the addition of a prime symbol. The system of FIG. 5 is identical to that of FIG. 4, and operates identically, except that winding 268 of signaling relay 17% is inserted in the primary gauging branch of the circuit, between the gauge and the transmitter 164, winding 168 being totally insulated from the bimetallic member. The effect of the insertion resistance of winding 16$ in the gauging circuit of FIG. 5 tends to be greater than it is in the arrangement of PEG. 4. Hence, while not necessary, it is advantageous to design and calibrate the magnetic gauge unit 164) to compensate for this insertion resistance, in order that error-free operation may be achieved. Again, however, the signaling relay is properly compensated for variations in the voltage of the supply and is or may be compensated for ambient temperature varaitions. While the arrangement of FIG. 5 is predicated upon the use of a signaling relay in a gauging circuit for detecting the level of gasoline in the tank, it will be apparent that the arrangement may be modified in accordance with the tcachin s of FIG. 4 or the knowledge in the art to permit the gauging or any other condition which may become critical in the apparatus, such as an automobile, with which the system is associated.

Fl". 6 of the drawings discloses one method of associating av si naling relay with a magnetic-type gauging system in which the condition to be sensed is denoted by low or minimum amplitude of current in the gauging circuit. In this system, the closure of switch 26% connects source 2% to the bimetallic or polymetallic element of signaling relay 2% and, hence across winding 2% mounted upon leg 2%. Que end of heater winding 21%, mounted upon or wound around leg 212, is connected to the bimetal element and, hence, through switch Ztlil to source 262, and the other end of winding 210 is connected to ground, over one path, through coil 214 of the magnetic gauge unit 216 and, over another path, through coil 2123 of unit 216 and variable resistor 22d. For purposes of illustration, resistor has been shown to be variable as a function of the level of gasoline in the tank, under the control of float 222, but in this case, low gasoline level results in a maximum value of resistance of resistor 22E? so that the critical condition to be sensed-Jew gasoline supply-is that of minimum current in the circuit including winding 210 and coil 218. As a emit, a some what larger resistance heater winding 21% must be employed than is the case in thesystem of FIG. 4, for example, but it has been found that with existing gauging systems adequate Wattage may be obtained to permit proper operation of the signaling relay 2% without varying the calibration accuracy of the gauge 215 to an extent detectable by the driver. For example, in one pragmatic application, the insertion of the signal relay was found to produce a change in the calibration of the gauge Zlti of about 2%.

In the arrangement of FIG. 6, the two metal strips forming the bimetallic element are assumed to be reversed, or the entire unit inverted, with respect to the unit of FIG. 4 so that the application of heat to leg 21?; Jill tend to move contact 224 away from contact .26, whereas the application of heat to leg 20:; will tend to move contact 2242 toward contact 226. Contacts 224 and 226 are in engagement when switch 2hr) is open. Upon the closure of switch 2%, the application of heat to leg 212 by winding 219 will produce a separation of contacts 224 and 226,

assuming a critical condition does not exist, and winding 2% will operate as a voltage compensating winding in the same fashion as previously described. It, at any time, contact 2% is closed to contact 226 for the requisite interval or for the requisite percentage of a preselected interval, integrating relay 228 will bring contact 2349 into engagement with contact 232 to energize the signaling or control device 234.

T e arrangement of PEG. 7 is similar to that of FIG. 6 except that the signaling relay is placed in the gauging branch circuit, and similar reference characters are applied to corresponding parts, a prime mark being affixed to the characters of FIG. 7. The sensing heater winding 21% of signal relay 204 is connected in series between the coil 218 of the gauge 216' and resistor 2-20, neither end of winding 210 being connected directly to the bimet-al or directly to the course of potential 202'. The operation of the arrangement of FIG. 7 is identical to that of FIG. 6, except for the noted difference in the point of interposition of the signaling relay in the gauging circuit and except for the provision of an additional winding 238 and an additional pair of contacts 240 and 242 on relay 204-. Contact 240 is mounted upon the free end of leg 212' on the opposite side thereof from contact 224'. However, contact 240 is insulated from portion 212. Contact 240 is normally separated from but is engageable with an electrical contact 242, and heater winding 258 is connected between coil 218' of gauge 216' and contact 242.

As previously noted with respect to FIG. 6 of the drawings, at the critical condition which is to be sensed and signaled, the value of resistor 22% is at or is approaching its maximum value. Hence, even though the resistance of winding 216 must be larger than in the cases of FIGS. 4 and to provide the requisite wattage at the low-current condition to operate the signal relay 2G4, still the percentage of the total circuit resistance represented by winding 21ft is small at the critical condition. How'- cver, if the fuel tank is approaching a full condition, the value of resistor 220 is reduced to a relatively small value so that at that time the resistance of heater winding fill represents an appreciably larger percentage of the total circuit resistance. This tends to interfere with the calibration of gauge 21.6 at the upper or full end of the scale. By the provision of winding 23S and contacts 24% and 242, signaling relay 204 may be endowed with a variableimpedance characteristic so that the effects of its insertion are not as significant as would otherwise be the case. As the fuel level approaches the full condition, so that the value of resistor 22b is decreased, the current through heater winding 2ft) is increased. At some selected current amplitude, leg 212 is deflected adequately to bring contact 2% into engagement with contact 242, whereupon winding 238 is connected in parallel with winding 2.116; in the gauging circuit so as to reduce the total effective impedance of the signal relay in the gauging circuit. This paralleling connection will also reduce the total applied heat to leg 1312' so that contact will tend to separate from contact 7.42, but upon such separation, the heating effect is increased so that contact 246 Will again be brought into engagement with contact 24-2. Gver a selectcd range of current amplitudes in the gauging circuit, therefore, contacts and 2.42 may be maintained in a condition of incipient opening and closing to adjust the effective insertion impedance of the relay 2d to mini mize the effect thereof upon the calibration of gauge 21s. At levels of current in excess of this range, contact will or may remain in engagement with contact 242 so that the insertion resistance is maintained at a steady, low value at or near the full scale position of gauge 216. As a result, calibration of gauge M6 throughout its range may be maintained within close limits despite the interposition of the signaling relay in the gauging circuit. The signal relay is preferably employed with gauging devices having viscous or other damping to reduce needle flutter from car vibration, gasoline splash,

etc.

It will be appreciated that the previously noted modifications of the relay structures, per se, are also applicable to the relay structures of FIGS. 47.

In the arrangement of FIG. 8 a dual-winding, bidirectionally control-led relay is provided which has three discrete operational positions and which is adapted to operate as a control device in, for example, a servo system. Relay 25%) comprises a pair of spaced-apart legs or portions 252 and 254 interjoined by a crosspiece 256 which is rendered relatively inflexible by any suitable means such as a flange 258. The unit is or may be ambient-temperature compensated. The end sea of portion 252 is fixed with respect to a first reference surface (which may itself be movable with respect to another reference surface), in a manner hereinafter to be described. The free end of leg portion 254 carries a pair of contacts 262. and 264 both of which are electrically and mechanically integral with portion 254. Contact 262 is mateable with an electrical contact 266 and contact sea is mateable with an electrical contact 268, both of the contacts 266 and 263 being fixed or adjustably fixed with respect to a reference surface (which may be fixed or movable with respect to the noted first reference surface). Heating means in the form of a winding 27d are mounted in heat transfer relation with portion 252, with one end of the winding 27% being electrically connected to portion sea, the entire bimetallic or polymetallic element being connected to ground. A heater winding 272 is mounted in heat transfer relation with portion 254, with one end of that winding being connected to portion 25d, and, hence, to ground. Representatively, the metal having the higher thermal coe cient of linear expansion is mounted on the upper surface of the element 2% so that elevation of the temperature of portion 252 will tend to move contact 262 upwardly into engagement with contact 266, whereas elevation of the temperature of portion 254 will tend to move contact 264 downwardly into engagement with contact 268.

Element 258 is shown in FIG. 8 to be a constituent part of a control system, such as a closed loop servo system, adapted to respond to the movement of a lever or the rotation of a shaft, or other mechanical movement, to control an output device such as a motor. For example, the arrangement herein disclosed may be employed as an improvement of a portion of the system utilized to adjust the attitude or levelness of an automobile body with respect to its wheels under diverse load conditions. Such a system is disclosed in, for example, an article commencing on page of the February 1955 issue of the magazine entitled Electrical Manufacturing and entitled New Packard Features Electrical Serve in Torsion-Bar Suspension. In that representative arrangement, optimum operation of the torsion-bar suspension system is achieved if the normal or average torsion of the bars is maintained at a selected design value. The design value, however, must be selected in the light of an estimated average distribution of load in the automobile. in practice, actual load distributions frequently vary from the design load distribution. in consequence, it is desirable to provide a compensator system compris ng means for sensing the amount of torsion of one or both of the torsion bars and means responsive thereto for appropriately shifting the attitude of the automobile.

The amount of twist of one or both of the main torsion bars is communicated through a sensing lever to a con trol apparatus adapted to translate this input information into electrical control signals which are applied to two output conductors. These signals are employed to control the selective operation of a reversible motor. An improved form of that control apparatus is represented in FIGS. 9-11 of the accompanying drawings. In those figures, control lever 285) (FIG. 10) is adapted to be rotated through arcs in either direction and about the longitudinal axis of shaft 282 by means including a sensing lever (not shown). Shaft is rotatably supported within a sleeve 2% which is or may integrally cast with a base plate 286, being further supported with respect thereto by reinforcing webs and "i l? (FiGS. and 11). At its lower end, shaft is provided with a noncircuilar projection 2% (FIG. 10) by means of which shaft 232 and control lever 28% are securely interjoined. A washer 294, which may be of cork or similar material, for example, is inter-posed the control lever 23% and the lower surface of the sleeve Shaft 282 extends aoove the base plate is sccured its upper end to an actuator 2% (Pi-US. 9ll). A tubular drive member surrounds a portion of the shaft 232; between the base plate and the actuator 2%, but is capable of rotational movement relative to both the base plate ass and the shaft A coil spring is mounted upon a reduced-diameter portion of the drive member 2% and its two ends Eilill and fill l are disposed upon opposite sides of a projection 3M (FIG. 11) integral with a horizontally disposed arm w h is a part of the drive member 298. The spring ends and also embrace a finger 310 on the actuator A rigid plate of insulating material is firmly secured to the arm 3% and carries a pair of spaced apart-cont act bearing arms and are extending downwardly therefrom. Arm 314 is engageable with a stop member 318 and arm 3.26 is engageable with a stop member both of which are rigidly secured to the base plate but electrically insulated therefrom.

Upon arcuate movement of control and hence, of shalt the rotational motion is communicated through actuator and its finger h to the coil spring Still, with that spri moving projection and hence arm on the drive member tension of the spring is such that any rotation of the shaft 2.32 will be comm" ed through the described train to move arm 3%:3, insulating plate 312 and depending arms Bird and until such tine as arm ""l or 316 strikes stop or Upon that event, any further rotation of the shaft 232 will only be applied to spring 369, with the arm 3%, the insulating plate 312 and the depending arms Ell-t and remaining at their limit position. If desired, means may be provided for establishing a limit to the maximum rotation of shaft 282 in either direction. For example, a rod 32 i (FIGS. 9 and 10), secured to the shaft 282, may extend through a slot 326 in the "do of the drive member and be engageable with stop pins 330 and 332 (FIG. 9) secured to the b so plate A contact 34- is mounted upon an arm 33d (FIGS. 10 and ll) ecured upon the base plate Arm 336 is insulated from base plate 285 but is electrically integral with terminal 33%. Contact 334 is positioned, by bending arm 3355, so that contact 3Y1 on depending arm 314 will engage contact 334; before depending arm 316 strikes stop 32%, and so that contact 319 on depending arm 316 will engage contact 334 before depending arm 314- strikes stop 3%. The electrical effect of the engagement of these contacts will be described hereinafter.

One end of the element (previously described with reference to FIG. 8) is secured to an upstanding portion 3% on the arm 3%, so that the element lies generally in a vertical plane with the contacts 262 and 26 i carried thereby normally lying at a point intermediate contacts and 26% (FIGS. 8 and 10), contactzt o being supported upon an arm and with contact 265 eing supported upon an arm 344-. Arms and 344 are secured to but insulated from the base plate 286.

The previously described arcuate motion of arm 1W8 will shift the position of element 25% so as to bring the contact or 264 thereon closer to the contact ass or Zoo with which it is to meet, in accordance with the direction of rotation of shaft 232, but this mechanical movement will not cause contact 262 to engage contact M6 la a,

nor will it cause contact to engage contact 6 3, energization of one or the other of the windings 27% or ZlZ on the element being required to cause engagement of one or the other of these pairs of contacts.

A pair of relays 343 and 35% is mounted upon a bracket o c to the base plate 236, and these relays, the bimetallic or polymetailic element and the windings thereon, the contacts and 2-53, the fired contact 334 and contacts and 319 on depending arms 314 and are electrical .y h er connected in the fashion shown in FIG. 8 of the drawings.

As is shown in r 16. 8, the relatively nsed contact 334 is connected to a source of potential 356, which may represent voltage supply system of an automobile, through a switch which may 1 e the automobiles ignition switch.

Whenever contact is contact M the moved into engagement with we, this voltage is applied via conductor 36!) to the heater winding 27%, the other end of which is connected to ground. The energization of winding 270 will ser e to elevate the temperature of leg 252, tending to move contact toward and into engagement with The thermal delay between the time of contact 3ft? to contact 534 and the closure of to contact may be selectsu in accordance desired operating conditions. This time delay, which may be, for example, in the order of sir; seconds, permits the system to be insensitive to transient shifts in position or attitude of the automobile so that corrective action will be taken only in response to a continuing condition, such as an increased or decreased loading of the vehicle.

Vvildll contact 2&2 engages contact 23-66 a circuit is completed from the source of potential sse, switch 3525, contacts and 317', winding of relay 3- 58, contacts 266 and 262, and through the bimetallic element to ground at the end 260 thereof. in response to this energization of its winding, relay 348 closes its No. 1 contacts to complete a sealing or locking circuit for itself since the armature ele ment of that pair of contacts is connected to ground. Relay S ill, in opening, also closes its No. 2 contact to apply ground to conductor 362 as one of two output signals.

if, alternatively, contact 319 is moved into engagement with contact 334, a circuit is completed from source 356, switch 353, contacts and 319, Winding of relay 2554i, conductor 3'64 and through the heater winding 272, the other end of which is connected to the element 25:? and, hence, is connected to ground. As a result, the heater winding 272 is energized in series with the winding of relay The resulting current is inadequate to cause the operation of relay $59 but is adequate to sufiiciently energize Winding 272 to cause leg portion 254 of element 2% to be deflected downwardly to bring contact into engagement with contact 26% after a selected delay interval, such as the aforesaid six seconds. T he closure of contact to contact 26? connects ground to conductor so that the winding of relay 3% is effectively connected directly across the voltage source 356, operating relay 356. Relay 35d, in operating, closes its No. 1 contact to complete a looking or sealing circuit for itself and closes its No. 2 contact to apply ground to conductor 3.56 to transmit the other of the two output signals. lit will be observed that the closure of contact 64 to contact 2568 establishes a shunt across heater winding 272 so that leg 254 will commence to cool to separate contact from contact However, prior to the time of this separation, relay 3% will have operated and locked or sealed operated.

As representative parameters, the source 356 may have a nominal output voltage of twelve volts, winding Z'lil may be 92 ohms, winding may be 42 ohms, and relays and may be provided with iii-ohm windings.

The output signals on conductors 362 and 365 are adapted to control the extent and the direction of rota- 17 tion of a motor 368 which is mechanically connected, in a manner not shown, to correct the condition which created the input signal to the system. In practice, as shown in the above-referenced article, the signals on conductors 362 and 366 are employed to actuate intermediate relays since the motor-current amplitudes are quite high.

While it will be apparent that the embodiments of the invention herein disclosed are well calculated to fillfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope of fair meaning of the subjoined claims.

What is claimed is:

1. In a system for association with a source of energy having a voltage which may vary a manually actuatable on-off switch controlling the energization of the system from the source, a thermally responsive device comprising an element at least a part of which is bendable in response to applied heat, first heater means for said element and energizable from the source of energy to deflect a portion of said element in one direction, means including a current modulating condition responsive element responsive to variations in a condition for controlling the current through said first heater means in accordance with variations in the condition being sensed and independent of changes in the position of said element of said device, and means for effectively compensating said device for the effects of variations of the voltage of the source and for reducing the effects of such variations on the position of said portion of said element of said device comprising second, voltage-variation compensating heater means for said element of said device and energizable from the source of energy to deflect said portion of said element of said device in a direction opposite to said one direction, and means including said switch for connecting said voltage-variation compensating heater means for continuous energization from the source of energy to a degree independent of the position of said portion of said element of said device.

2. The combination of claim 1 further characterized in that both said first and second heater means are electrical windings disposed in heat transfer relation with said element and in that said second heater means is a voltage variation compensating winding.

3. The combination of claim 1 further including an integrating thermal relay having an energizing winding connected in circuit with said current modulating condition responsive means and a pair of contacts controlling said first heater winding means.

4. The combination of claim 1 further including a signal device, and an integrating thermal relay having an energizing winding controlled by said thermally responsive device and having a pair of electrical contacts controlling said signal device.

5. The combination of claim 1 further characterized in that said first and second heater means heat different parts of said element and in that the extent of energization of said second heater means is independent of variations of said current modulating condition responsive element.

6. The combination of claim 1 further characterized in that said first and second heater means heat different parts of said element, and in that said first and second heater means respond similarly to a given change in voltage of the source of energy to tend to deflect said portion of said element concurrently in opposite directions so as to minimize the eiiect of the change of the voltage of the source of energy upon the position of said portion of said element.

7. In a gauging system, a source of voltage, a current modulating sensing device for varying current as a continuous function of variations of a condition which it is sensing, a gauging element for gauging said variations of current and having a sensing winding and a voltagevariation compensating winding, a signal relay having a sensing winding and a voltage-variation compensating winding and a pair of contacts having open and closed states, means connecting said source, said device and said sensing windings in circuit with one another, and means connecting said voltage-variation compensating windings for continuous energization from the source to a degree independent of the state of said contacts.

8. The combination of claim 7 further including a timedelay device controlled by said relay and an alarm device controlled by said time-delay device.

9. The combination of claim 7 further including means for varying the effective insertion impedance of said relay in said circuit.

10. In a gauging system, a source of voltage, a current modulating sensing device for varying current as a continuous function of variations of a condition which it is sensing, a gauging element for gauging said variations of current and having a sensing winding and a voltage-variation compensating winding acting in opposition to one another upon a movable element, a signal relay having a sensing winding and a voltage-variation compensating winding acting in opposition to one another upon a movable element and a pair of contacts controlled by said element and having open and closed states, means connecting said source, said device and said sensing windings in circuit with one another, and means connecting said voltage-variation compensating windings for continuous energization from thesource to a degree independent of the state of said contacts.

11. In a control system energizable from a source of voltage the average value of which tends to vary for controlling the relative positions of a pair of cooperating electrical contacts in accordance with the temperature of a body which is heated through a range of temperatures, the combination of a variable-resistance senser having a substantial temperature coefiicient of resistance disposable in heat transfer relation with the body, first and second poly metallic portions conjointly controlling the relative positions of said electrical contacts, heating of one of said portions tending to produce relative movement of said electrical contacts in one direction, heating of the other one of said portions tending to produce relative movement of said electrical contacts in the opposite directiomfirst electrically energizable heating means for said first portion, second electrically energizable voltage-variation compensating heating means for said second portion, means connnecting said sensor in circuit with said first heating means and to the source for varying the current in said first heating means with variations of the temperature of the body over the range of temperatures, and means connecting said voltage-variation compensating second heating means for continuous energization from the source to a degree independent of the position of said contacts for reducing the eiiects upon the relative positions of said electrical contacts of changes in heating of said first heating means resulting from variations in the average value of the voltage of the source.

12. The combination of claim 11 further including an electrically energizable load device, and means for controlling the actuation of said load device in accordance with the temperature of the body comprising an electrically energizable relay for controlling the actuation of said load device, and circuit means connecting said electrical contacts in circuit with said relay.

13. The combination of claim 11 in which the energizetion of both of said first and second heating means is independent of changes of the relative positions of said electrical contacts.

14. The combination of claim 11 in which said first and second polymetallic portions are substantially parallel leg portions of a generally U-shaped element with the free end of one of the portions being supported and with the free end of the other one of the portions controlling the position of one of said electrical contacts.

15. The combination of claim 11 further including means including third electric-ally energizable heating means and effective upon the engagement of said electrical contacts for changing the heating of one of said portions in a direction to separate said contacts and effective upon the resultant separation of said electrical contacts for changing the heating of that portion in a direction to cause said contacts to reengage to producepulsing operation of said electrical contacts.

16. In a system for association with a source of energy having a voltage which may vary,a manually actuatable on-oif switch controlling the energiaztion of the system from the source, a thermally responsive device comprising an element at least a part of which is bendable in response in applied heat, first heater means for said element and energizable from the source of energy to deflect a portion of said element in one direction, means including a temperature sensing resistor having a substantial temperature coefiicient of resistance responsive to variations of sensed temperature for controlling the current through said first heater means in accordance with variations in the sensed temperature and independent of changes in the position of said element of said device, second, voltage-variation compensating heater means for said element and energizable to deflect said portion of said element in a direction opposite to said one direction for reducing the effects upon said portion of said element of changes in heating of said first heater means resulting from variations of thevoltage of the source, means including said switchlfor connecting said second, voltage-variation compensating heater means for continuous energization from the source of energy to a degree independent of changes in the position of said portion of said element, a pair of electrical contacts having opened and closed states controlled by saidportion of said element, and means including third electrically energizable heater means effective over a range of variations of the current through said first heater means and upon the change of state of said electrical contacts for changing the heating of one of said portionsin a direction to oppositely change the state of said contacts and effective upon the resultant change of state of said electrical contacts for changing the heating of that portion in a direction to cause said contacts to again change state to produce pulsing operation of said electrical contacts. i

17. In a control system energizable from a source of voltage the average value of which tends to vary for con trolling the relative positions of a pair of cooperating electrical contacts in accordance with the temperature of a body which is heated through a range of temperatures, the combination of a variable-resistance senser having a substantial temperature coetficient of resistance disposable in heat transfer relation with the body, first and second polymetallic portions conjointly controlling the relative positions of said electrical contacts, heating of one of said portions tending to produce relative movement of said electrical contacts in one direction, heating of the other one of said portions tending to produce relative movement of said electrical contacts in the opposite direction, first electrically energizable heating means for said first portion, second, voltage-variation compensating electrically energizable heating means for said second portion, means connecting said senser in circuit with said first heating means and to the source for varying the current in said first heat ing means with variations of the temperature of the body over the range of temperatures, and means connecting said second, voltage-variation compensating heating means for continuous energization from the source to a degree independent of the position of said contacts and independent of variations in the resistance of said variable-resistance senser for reducing the elfects upon the relative positions of said electrical contacts of changes in heating of said first heating means resulting fromv variations in the average value of the voltage of the source.

References Cited in the file of this patent UNITED STATES PATENTS 2,275,237 Smulski Mar. 3,, 1942 2,285,677 Myers lune 9, 1942 2,519,368 Halleroerg Aug. 22, 1950 2,571,360 Hallerberg Oct. 16, 1951 2,654,865 Klug Oct. 6, 1953 2,762,997 Boddy Sept. 11, 1956 3,010,097 Boddy Nov. 21, 1961 

7. IN A GUAGING SYSTEM, A SOURCE OF VOLTAGE, A CURRENT MODULATING SENSING DEVICE FOR VARYING CURRENT AS A CONTINUOUS FUNCTION OF VARATIONS OF A CONDITION WHICH IT IS SENSING, A GAUGING ELEMENT FOR GAUGING SAID VARIATIONS OF CURRENT AND HAVING A SENSING WINDING AND A VOLTAGEVARIATION COMPENSATING WINDING, A SIGNAL RELAY HAVING A SENSING WINDING AND A VOLTAGE-VARIATION COMPENSATING WINDING AND A PAIR OF CONTACTS HAVING OPEN AND CLOSED STATES, MEANS CONNECTING SAID SOURCES, SAID DEVICE AND SAID SENSING WINDINGS IN CIRCUIT WITH ONE ANOTHER, AND MEANS CONNECTING SAID VOLTAGE-VARIATION COMPENSATING WINDINGS FOR CONTINUOUS ENERGIZATION FROM THE SOURCE TO A DEGREE INDEPENDENT OF THE STATE OF CONTACTS. 